The present invention relates to a lift device and, more particularly, to a self-contained lifting assembly which is especially suitable for use in a transfer assembly of a conveyor system.
Transfer assemblies are typically positioned between two conveyor sections and are adjacent one or more transfer conveyors for selectively transferring loads carried by the conveyor sections to one of the transfer conveyors. Transfer assemblies include a group of conveying components, such as rollers, belts, wheels or the like, which provide a conveying surface for one or more loads and move the loads in a conveying direction between the two conveyor sections. Positioned between one or more of the conveying components are transferring components, such as belts, rollers, wheels or the like, which are oriented such that they move laterally with respect to the conveying direction of the conveying components to selectively transfer a load or loads in a direction lateral to the conveying direction. The transferring components are selectively raised to lift a load (or loads) off the conveying surface of the conveying components to move the load laterally with respect to the conveying surface onto the adjacent transfer conveyor. This is alternately achieved by lowering the conveying components. Typical combinations of conveying components and transferring components in transfer assemblies include: Belts or chains with intermediate rollers or wheels; wheels with intermediate belts, chains, or rollers; or rollers with intermediate belts, chains, or wheels.
When a transfer is to take place, the transferring components are raised by an actuator so that the load or loads are raised above the conveying surface of the conveying components. In the case of conveying components that are lowered, an actuator is used to lower the conveying components so that the load or loads are then deposited on the transferring components. Heretofore, these actuators have typically comprised pneumatic actuators. While pneumatic actuators are relatively inexpensive, they require a source of air and, further, provide an abrupt movement which results in dynamic loading of the various component parts forming the transfer assembly and of the actuator itself.
It is therefore an object of this invention to provide an actuator or lifting device that can provide a smooth lifting and lowering motion and, further, offers a non-pneumatic application, thus, eliminating the need for a supply of air. In addition, in order to offer a lifting device with greater flexibility and, therefore, broader application, there is a need for a lifting device which is compact and preferably modular.
According to the present invention, a compact modular lifting/lowering device is provided that offers a smooth lifting or lowering motion by moving the support surface at varying speeds to minimize the sudden acceleration and deceleration of the transferring components.
In one form of the invention, a lift assembly for raising and lowering a load includes a first member, which is adapted for resting on a reference surface, and a second member which defines a support surface for supporting a load. A drive assembly selectively moves the second member relative to the first member from an initial position to a final position to raise or lower the second member relative to the first member. The drive assembly is adapted to move the second member from its initial position at a progressively increasing speed to an intermediate position and after which at a progressively decreasing speed until the second member is moved to its final position.
In one aspect, the drive assembly preferably moves the second member relative to the first member at speeds having a sinusoidal profile.
In other aspects, the drive assembly includes a motor and at least one crank arm, which is coupled to the second member. The motor moves the crank arm in a semicircular path to thereby raise or lower the second member relative to the first member at the variable speeds. Preferably, the driver includes at least one driver shaft, with the crank arm being coupled to the driver shaft and the motor driving the driver shaft to thereby move the crank arm.
In further aspects, the drive assembly includes a second driver shaft and a second crank arm which is coupled to the second driver shaft. The second crank arm is coupled to the second member and, further, coupled to the first driver shaft. Thus, when the motor drives the first driver shaft, which in turn drives the second driver shaft, the first and second crank arms are moved in a semicircular path to thereby move the second member.
In another aspect, the first and second members are nested to thereby form a compartment therein. For example, each of the first and second members includes an inwardly depending flange to thereby form the compartment therebetween. In preferred form, the drive assembly is positioned in the compartment and, more preferably, fully contained in the compartment.
In addition, at least one spring may be housed in the compartment, which is in a compressed state when the second member is moved to a retracted position whereby the spring reduces the load on the drive assembly when the drive assembly moves the second member to an extended position.
According to another form of the invention, a lift assembly for raising and lowering a load includes a first member, a second member, and a drive assembly as noted above. The first member and the second member are defined in a compartment therebetween in which the drive assembly is positioned and contained. The drive assembly selectively moves the second member relative to the first member from an initial position to a final position to raise or lower the second member relative to the first member. In addition, the drive assembly includes a motor and a crank arm, which is adapted to move the second member at speeds having a sinusoidal profile wherein the second member moves from the initial at a progressively increasing speed to an intermediate position and after which at a progressively decreasing speed until the second member is moved to its final position.
In other aspects, the motor moves the crank arm in a semicircular path to thereby raise or lower the second member relative to the first member. In further aspects, the drive assembly further includes a guide and a track secured to the second member. The guide is positioned in the track and coupled to the crank arm and moves along the track when the crank arm is moved in its semicircular path thereby moving the second member between its initial and final positions.
In a further aspect, the drive assembly further includes at lease one driver shaft and a pair of crank arms. The crank arms are coupled to the driver shaft with the motor driving the driver shaft to move the crank arms in a semicircular path to thereby move the second member.
According to yet another form of the invention, a lift assembly for raising and lowering a load includes a first member, second member, and a drive assembly as noted above. The drive assembly moves the second member along an axis of extension relative to the first member from an initial position to a final position to raise or lower the second member relative to the first member. The first member is substantially rigidly coupled to the second member in directions lateral to the axis of extension, with the drive assembly being adapted to move the second member in the axis of extension from the initial position at a progressively increasing speed to an intermediate position and after which at a progressively decreasing speed until the second member is moved to its final position. In addition, the drive assembly couples the first member to the second member in the axis of extension.
In further aspects, the drive assembly preferably moves the second member relative to the first member at speeds having sinusoidal profile.
These and other objects, advantages, purposes, and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings.